RESURFACING VS METAL-ON-METAL HIP ARTHROPLASTY: IS DECAPITATION JUSTIFIED? – A STUDY OF 450 PATIENTS

Abstract

The aim of this study was to compare the clinical outcome, radiological outcome, activity level and functional outcome of hip resurfacing against metal on metal (MOM) hip arthroplasty.

Matched pairs of patients were selected from consecutive patients who had either MOM arthroplasty (n=236) or hip resurfacing (n=264). We matched 346 patients (173 pairs) in terms of age, sex, diagnosis, and a minimum follow up of 60 months. The functional outcome was assessed using Harris, Charnley-MDP, SF-36, UCLA and Tegner scores. Mean follow up was 67 months (61–80).

Mean age was 54.5 years. Femoral neck fractures were seen in 4 patients in the resurfacing group. The mean acetabular inclination was 42.8 deg and 44.3 deg in the resurfacing and MOM groups. Mean stem subsidence was 1.2mm. Bony ingrowth was seen in ninety six stems and all stems were stable by Engh s criterion. Radiolucent halo was observed around the stem of two resurfacing heads. The mean Harris hip score was 87.9 and 88.2 in the MOM and resurfacing groups respectively (p=0.76). The SF 36 score was 77.8 and 80.1 (p=0.4). The UCLA and Tegner scores were 6.1 and 3.6 for the resurfacing group and 5.9 and 3.9 for the MOM group. Nine patients in the resurfacing group had a postoperative painful limp which settled by 3 months. There was no radiological evidence of implant failure at last follow up. Survival at 5 years was 100% for the MOM group and 94.1% for the resurfacing group.

Functional outcome and activity levels increased in both groups with no difference between the groups. Post operative complications were fewer in MOM group and return to activity was quicker. It appears that resurfacing arthroplasty offers no medium term advantages over MOM arthroplasty. However longer follow up is required to establish the longevity and durability of this implant.